Ernest H. Carlson

Celestite replacements of evaporites in the Salina Group

Abstract Replacements of evaporites by celestite were discovered recently at three sites in northwestern Ohio. These replacements are more durable than the original evaporites and provide new paleoenvironmental data for the upper Silurian rocks of the region. The occurrences are situated along the western margin of the Ohio (Cayugan) Basin and appear in the Greenfield Dolomite and in undifferentiated Salina dolostones. The replacements include: lenticular and prismatic crystals of gypsum, nodules of anhydrite and laminar evaporites. The lenticular crystals contain inclusions of carbonate and anhydrite, and are believed to have altered to anhydrite prior to replacement. The prismatic crystals are exceptionally well-preserved, with euhedral, deeply embayed outlines and internally zoned growth bands containing large numbers of inclusions of dolostone and anhydrite. Optical data for the latter crystals indicate that they are oriented replacements of gypsum, and suggest that the original gypsum was unchanged prior to replacement. The nodular and laminar occurrences display features such as chicken-wire and enterolithic structures, and were comprised of anhydrite prior to replacement. Replacement postdates the dolomitization and cementation of the Salina sediments enclosing the evaporites, but occurred prior to deep burial. The rocks hosting the replacements, therefore, did not provide the strontium. The strontium may have been released from dolomitization of the underlying Lockport (Niagaran) beds or from dissolution of subaerially exposed Salina gypsum prior to the middle Devonian.

Paleoshoreline patterns in the transgressive-regressive sequences of Pennsylvanian rocks in the northern Appalachian Basin, U.S.A.

Abstract Sheets of sponge spicule flint of Pennsylvanian age (Bashkirian, Moscovian, Kasimovian) that are present in the northern Appalachian Basin of Ohio and adjacent parts of Kentucky, Pennsylvania and West Virginia, are important indicators of paleoshorelines. This flint typically occurs with or occupies the position normally held by shallow-water limestone and contains a normal marine fauna. The flint was deposited above coal or underclay, representing the detritus-starved marine portion of a transgressive-regressive sequence and marking the eastern limit of transgression across a westward-spreading alluvial plain. Flint occurs at several stratigraphic positions in the upper Pottsville-lower Conemaugh interval. The most important are: Boggs, Upper Mercer and Kanawha flints of the upper Pottsville Group; Kilgore-Flint Ridge, Zaleski and Vanport flints of the lower Allegheny Group; and Brush Creek flint of the lower Conemaugh Group. Lithofacies maps of these beds were constructed to show the distribution of the flint. Limestone-hosted flint occurs in long discontinuous chains of sheetlike bodies, whereas shale-hosted flint occurs in single sheets with restricted geographic distribution. Chains of limestone-hosted flint attain maximum dimensions of a few meters in thickness, a few kilometers in width and several hundreds of kilometers in length. The Upper Mercer, Vanport and Brush Creek flints are particularly extensive, forming arcuate shoreline patterns that parallel the fronts of large delta systems. Beds of clay ironstone and/or coal above flint indicate that the lagoonal environment in which flint was deposited was followed closely by a change to stagnant waters. Cementation of flint with silica likely occurred under the lower pH conditions existing at that time and when depths of burial were shallow.

Regional hydrogeochemical patterns in ground water of Northwestern Ohio and their relation to Mississippi valley—type mineral occurrences☆

ABSTRACT Deering, M.F., Mohr, E.T., Sypniewski, B.F. and Carlson, E.H., 1983. Regional hydrogeochemical patterns in ground water of northwestern Ohio and their relation to Mississippi Valley-type mineral occurrences. In: G.R. Parslow (Editor), Geochemical Exploration 1982. J. Geochem. Explor., 19: 225–241. A cluster of minor Mississippi Valley-type deposits occurs in northwestern Ohio. The district, which forms a northeasterly trending belt that cuts across the Findlay Arch, extends from the Indiana border to the Lake Erie Islands. The minerals of the deposits — chiefly celestite, fluorite and sphalerite with lesser amounts of barite and galena — show variation in both geographic and stratigraphic distribution. Dolomites of Middle Silurian to Middle Devonian age, which are the host rocks, also form an important aquifer system. The deposits are of interest because they might be indicators of economic mineralization at depth. Through a reconnaissance study, one-hundred ground-water samples from shallow wells (less than 50 m deep) were collected across an area of approximately 19 000 km2. Recharge takes place in the southern part of the area while ground-water flow is northward towards Lake Erie. The majority of the samples are high in sulfate with the source being evaporites within the carbonate sequence. The remainder of the water samples are rich in bicarbonate. Trend surface maps for the major constituents indicate that the ground-water chemistry for the region is established chiefly by the lithology and the flow system. Trend surface maps for F−, Sr and Ba reflect the geographic distribution of the minerals in the deposits. Correlations are weakened, however, due to the influence of geochemical barriers such as SO42- on Ba and Sr, and Ca on F−. The map for Pb follows the trends of the major constituents instead of the mineralization. In a detailed study across northwestern Sandusky County, which lies near the center of the district, 46 samples were collected in an area of 78 km2. Trend surface maps for Ca, Mg, SO42- and total dissolved solids reflect the chemistry of the bedrock and display concentrations that increase along the local flow path. Maps for F−, Sr and Ba correlate with mineralization in the vicinity, the first of these displaying a local trend and the last two correlating with regional trends.

Vapor phase crystal growth in the system PbS-Bi2S3

Abstract An investigation of crystal growth in the system PbS-Bi2S3 was made by vapor phase techniques, using the closed tube method. For most experiments the source was held at 746 °C and the growth region was maintained at about 670 °C. Cubic crystals of PbS were obtained. Prismatic crystals of the following phases: Phase II (6Pb1−xBi2x/3S·Bi2S3), Phase III (3Pb1−xBi2x/3S·Bi2S3), Phase IV (Pb1−xBi2x/3S·Bi2S3) and Bi2S3 were acquired. Crystal growth was achieved by utilizing I2 and NH4Cl as transporters, and by volatilization under vacuum. A comparison of the magnitude of the transport rates obtained by these three methods was made. For Bi2S3 growth in I2, the curve plotting the variation of the transport rate with I2 concentration was found to show a maximum value. The highest rates were found for the transportation of Phase II, Phase III, Phase IV and Bi2S3 by I2; much lower rates were found for these same substances in NH4Cl and by volatilization. The moderate rates found for PbS in NH4Cl were higher than the corresponding rates in I2 and by volatilization. The largest crystals obtained for Phase II, Phase III, Phase IV and Bi2S3 were grown in I2; the largest PbS crystals were grown in NH4Cl. At temperatures lower than those employed for the main group of experiments, and using I2 as a transporter, crystals of Pb5S2I6 were grown in the case of Pb2, and crystals of Bi6.3IS9 in the case of Bi2S3. At a growth temperature of about 400 °C, NH4Cl was the only effective transporter for the phases in the system PbS-Bi2S3.

Re-examination of Hg pollution in the Ashtabula area, Astabula County, Ohio

Abstract Environmental concern about Hg pollution in Lake Erie peaked in 1970 with most investigations being directed to the west end of the lake and problems associated with Lake St. Clair. The Ohio Geological Survey subsequently (1970–1971) collected and analyzed stream and lake sediments in the vicinity of several industrial areas that border Lake Erie and reported indications of Hg pollution along the lower reaches of the Ashtabula River. Neither the intensity, nor the center, of the contamination was recognized in that study. In 1970, however, the state began to monitor the levels of Hg in the industrial effluent of the area. During a re-investigation of pollution at Ashtabula, 68 sediment samples were collected across an area of 90 km 2 in the late spring and early summer of 1982. The Hg that was released by heating the samples on a hot plate for one minute at 290°C was determined with a gold-film Hg detector. Mercury concentrations in the sediments had a median (background) value of 24.4 ppb and a mean content of 422 ppb, and exhibited a lognormal distribution that was bimodal. Three samples that ranged from 1550 to 20,600 ppb Hg are considered anomalous and come from the drainage of Fields Brook. Although no single industrial operation could be targeted as a source, high Hg levels apparently are due to the past accumulation of industrial waste. Mean Hg levels in the Ashtabula River samples from south and north of the junction with Fields Brook were 42.8 and 118.5 ppb Hg, respectively, indicating that contamination of the latter had occurred. The Lake Erie samples (mean ppb Hg) can be separated by the mouth of the Ashtabula River and the depth of the lake bottom as follows: west side (9.7), east side (59.8); and shoreline (15.8), nearshore (64.5). The six-fold increase on the eastern side of the harbor relative to the western side is believed to be due to the direction of the longshore currents which, in the Ashtabula area, run from southwest to northeast. The four-fold increase in Hg levels in nearshore sediments relative to those from the shoreline is due to preferential concentration in the finer size fraction. The Hg levels obtained for nearshore sediments just east of the Ashtabula River are six times higher than those reported earlier by the Geological Survey, suggesting that accumulation of Hg may have occurred.

Mineralogy and Paragenesis of Large Dolostone Septaria: In the Late Devonian Huron Shale, North-Central Ohio

limited parking is available along the berms. No-trespassing signs are posted at other river crossings. East Branch sites are reached from the bridge at Lovers Lane by going downstream 0.5 kilometer to the junction of the West and East branches and following the East Branch upstream. Collecting sites along the river are discovered by partial trails and by wading. The river is treacherous after a rain, and access is limited to low-water stages, usually in summer and fall. Because the septaria are tough, large sledgehammers and chisels are required to open them. Early geologists working along the Huron River first noted the large concretions (Newberry 1870, 1874; Read 1878; Prosser 1913); the vein minerals of the septaria were originally described by Read (1878) and much later by Hyde and Landy (1966) and by Leavens (1968). Organic remains, IN THE LATE DEVONIAN HURON SHALE, NORTH-CENTRAL OHIO

Reactivated interstratal karst—example from the Late Silurian rocks of western Lake Erie (U.S.A.)

Abstract Interstratal karst developed in the Late Silurian rocks of western Lake Erie that, after a long interruption, was exhumed and reactivated. The dissolution front of the G evaporite of the Salina Group receded in the downdip direction during these two well-documented periods of subaerial exposure. The karst features that developed in the overlying Bass Islands Dolomite (Pridolian) consist of a large tabular body of collapse breccia and a number of smaller features including breccia pipes, partially filled pipes, blister caves and collapse dolines. The tabular breccia body and the breccia pipes, which originated penecontemporaneously during post-Silurian and pre-Middle Devonian subaerial exposure, occur along the updip edge of the present outcrop belt of the dolostone. They are monolithologic, fragment-supported rubble breccias, with the pipes exhibiting a greater fragment displacement, rotation and rounding, and a smaller fragment size. The matrix sediment of the tabular body is a quartz sand, an equivalent of the basal sandstone that filtered down from the erosion surface. The presence in the matrix sediment of nodular celestite, a later replacement of evaporites that formed when the sediment was still soft, indicates that a sabkha environment existed at the time the breccia was infilled. The partially filled pipes, which form cylindrical caves that are lined with late diagenetic celestite, are believed to be cogenetic with the collapse breccias. The blister caves and dolines occur downdip from the breccias, postdating Pleistocene glaciation and predating isostatic rebound. These caves are isolated, crescent- or oval-shaped openings with domed roofs, averaging about 60 m in width and 4 m in height. The hydration and resulting expansion of lenticular bodies of anhydrite along the receding solution front of the G unit is believed to be the cause of doming. The numerous crescentic caves, originating from the dissolution of this gypsum and the subsequent collapse of the domed roofs, are expressed at the surface as shallow dolines.